1. Field of the Invention
This invention relates to a mixed metal oxide catalyst containing oxides of molybdenum, bismuth, iron, cesium and, optionally, other metals for the production of unsaturated aldehydes from olefins, such as methacrolein by gas phase catalytic oxidation of isobutylene in the presence of air or another gas containing molecular oxygen.
2. Description of the Prior Art
Many catalysts have been disclosed for use in the production of acrolein or methacrolein by catalytic vapor phase oxidation of propylene or isobutylene. U.S. Pat. No. 4,816,603 discloses a catalyst for production of methacrolein and methacrylic acid of the formula:MoaWbBicFedNieSbfXgYhZiAjOk where X is potassium, rubidium and/or cesium, Y is phosphorus, sulfur, silicon, selenium, germanium and/or boron, Z is zinc and/or lead, A is magnesium, cobalt, manganese and/or tin, a is 12, b is 0.001 to 2, c is 0.01 to 3, d is 0.01 to 8, e is 0.01 to 10, f is 0.01 to 5, g is 0.01 to 2, h is 0 to 5, i is 0.01 to 5, j is 0 to 10 and k is sufficient to satisfy the valences.
U.S. Pat. No. 4,511,671 discloses a catalyst for manufacturing methacrolein of the formula:MoaWbBicFedAeBfCgDhOx where A is at least one of nickel and/or cobalt; B is at least one of alkali metals, alkaline earth metals and/or thallium; C is at least one of phosphorus, tellurium, antimony, tin, cerium, lead, niobium, manganese and/or zinc; D is at least one of silicon, aluminum, zirconium, and/or titanium; a is 12, b is 0 to 10, c is 0.1 to 10, d is 0.1 to 20, e is 2 to 20, f is 0 to 10, g is 0 to 4, h is 0 to 30 and x is determined by the atomic valences.
U.S. Pat. No. 4,556,731 discloses a catalyst for production of methacrolein and methacrylic acid of the formula:AaBbFecXdMeMo12Ox where A is an alkali metal, such as potassium, rubidium, cesium or mixtures thereof, thallium, silver or mixtures thereof, B is cobalt, nickel, zinc, cadmium, beryllium, calcium, strontium, barium, radium or mixtures thereof, X is bismuth, tellurium or mixtures thereof and M is (1) Cr+W, Ge+W, Mn+Sb, Cr+P, Ge+P, Cu+W, Cu+Sn, Mn+Cr, Pr+W, Ce+W, Sn+Mn, Mn+Ge or combinations thereof, (2) Cr, Sb, Ce, Pn, Ge, B, Sn, Cu or combinations thereof, or (3) Mg+P, Mg+Cu, Mg+Cr, Mg+Cr+W, Mg+W, Mg+Sn or combinations thereof, a is 0 to 5, b is 0 to 20, c is 0 to 20, d is 0 to 20, e is 0.01 to 12 and x satisfies the valence requirements.
U.S. Pat. No. 5,245,083 discloses a catalyst for preparing methacrolein of a mixture of composition (1) of the formula:MoaBibFecXdZfOg where X is Ni and/or Co, Z is at least one of W, Be, Mg, S, Ca, Sr, Ba, Te, Se, Ce, Ge, Mn, Zn, Cr, Ag, Sb, Pb, As, B, P, Nb, Cu, Cd, Sn, Al, Zr and Ti, a is 12b is 0.1 to 10, c is 0 to 20, d is 0 to 20, f is 0 to 4 and g satisfies the valence requirement and composition (2) of the formula:AmMonOp where A is at least one of K, Rb and Cs, m is 2, n is 1 to 9 and p is 3n+1.
U.S. Pat. No. 5,138,100 discloses a catalyst for preparing methacrolein with a mixture of composition (1) of the formula:MoaBibFecXdYeZfOg where X is at least one of Ni and Co, Y is at least one of K, Rb, Cs and Ti, Z is at least one of the elements belonging to Groups 2, 3, 4, 5, 6, 7, 11, 12, 13, 14, 15 and 16, specifically beryllium, magnesium, calcium, strontium, barium, titanium, zirconium, cerium, niobium, chromium, tungsten, manganese, copper, silver, zinc, cadmium, boron, aluminum, germanium, tin, lead, phosphorus, arsenic, antimony, sulfur, selenium and tellurium, a is 12, b is 0.1 to 10, c is 0 to 20, d is 0 to 20, e is 0 to 2, f is 0 to 4, and g satisfies the valence requirement and composition (2) of the formula:LnhMoiOj 
where Ln is at least one of the rare earth elements, h is 0.2 to 1.5, i is 1 and j satisfies the valence requirement. The atomic ratio of the rare earth element to molybdenum is disclosed to be in the range from 0.2 to 1.5 with an atomic ratio less than 0.2 resulting in high selectivity but poor activity and with an atomic ratio greater than 1.5 resulting in high activity but poor selectivity.
U.S. Pat. No. 4,537,874 discloses a catalyst for production of unsaturated aldehydes of the formula:BiaWbFecModAeBfCgDhOx where A is nickel and/or cobalt, B is at least one of alkali metal, alkaline earth metals and thallium, C is at least one of phosphorus, arsenic, boron, antimony, tin, cerium, lead and niobium, D is at least one of silicon, aluminum, zirconium and titanium, a is 0.1 to 10.0, b is 0.5 to 10.0, c is 0.1 to 10.0, d is 12, e is 2.0 to 20.0, f is 0.001 to 10.0, g is 0 to 10.0 and h satisfies the valence requirement. The ratio of a/b is 0.01 to 6.0 so that bismuth is combined very stably with tungsten and compounds such as bismuth trioxide and bismuth molybdate are not formed.
U.S. Pat. No. 5,728,894 discloses a catalyst for producing methacrolein of the formula:Mo12BiaCebKcFedAeBfOg where A is Co or a mixture of Co and Mg having an atomic ratio of Mg to Co not more than 0.7, B is Rb, Cs or a mixture thereof, a is 0 to 8, b is 0 to 8, c is 0 to 1.2, d is 0 to 2.5, e is 1.0 to 12, f is 0 to 2.0, g satisfies the valence requirement. The relative atomic ratio of iron to bismuth and cerium should be 0<d/(a+b+d)≦0.9. The relative atomic ratio of bismuth, cerium and potassium should be 0.05≦b/(a+b+c)≦0.7. The relative atomic ratio of potassium to bismuth and cerium should be 0≦c/(a+b+c)≦0.4. Bismuth, cerium, potassium, iron and cobalt are indispensable elements for the disclosed invention.
U.S. Pat. No. 5,166,119 discloses a method for preparing a catalyst of molybdenum, bismuth, iron and cesium or thallium for producing methacrolein and methacrylic acid by gas phase catalytic oxidation of isobutylene or tert-butanol with molecular oxygen. There is no preference disclosed of cesium over thallium.
Prior art discloses mixed metal oxide catalysts which contain molybdenum, bismuth, iron, cesium and other metals for the production of methacrolein. Furthermore, prior art discloses certain ranges of amounts of these metals. Some prior art discloses relative ratios of certain components to other components. The effect of the selection of certain components for a mixed metal oxide catalyst for the production of methacrolein and the relative relationship of some of these components to other components has not been investigated in complete detail.